Real-time assay for quantitative detection of non-persistently transmitted Plum pox virus RNA targets in single aphids

A TaqMan real-time RT-PCR was developed to detect and quantify RNA-targets from the non-circulative, non-persistently transmitted Plum pox virus (PPV) in individual fresh or aphids captured previously and squashed on paper. Reliable quantitation ranged from 40 up to 4 × 108 copies of control transcripts. This technique was applied successfully to plant material and to individual PPV vector (Myzus persicae) and non-vector of PPV (Aphis nerii) aphid species demonstrating acquisition of viral targets by both vector and non-vector aphids. The number of viruliferous aphids detected by real-time RT-PCR and nested RT-PCR in a single closed tube was similar in parallel assays, nevertheless the sensitivity provided by real-time RT-PCR was 100 times higher than nested RT-PCR and 1000 times higher than DASI-ELISA and conventional RT-PCR. The quantities of PPV-RNA targets detected in a single aphid ranged from 40 to more than 2 × 103 units. The combined system (immobilization of targets on paper by squash capture and real-time RT-PCR) allows, for the first time, reliable quantitation of PPV targets acquired by individual aphid species and constitute an excellent tool for understanding better PPV epidemiology.